The XSLT specification is available from the World Wide Web Consortium web site at http://www.w3.org/TR/xslt.html. Reading the specification is a perfect cure for insomnia, so to keep you awake, I summarize key parts of XSLT here as they relate to Python.

In any working XSLT setup, three distinct files exist and at least one piece of software is utilized. The first is the source XML file, which is your original document. The next is the XSL stylesheet, which represents the rules of the transformation and is itself an XML-compliant document. The third and final document is the result of the transformation. This is most likely either HTML or XML. The essential software used to create the transformation is the XSLT processor. This software loads the original XML document, applies the transformation rules, and spits out the result of the transformation. Figure 6-1 shows an example of this arrangement.

Figure 6-1. The XSLT transformation process

The XSLT language is an XML-based language. It is defined as a set of elements and attributes with carefully defined semantics. XSLT is very straightforward, as you’ll discover.